The fusion of 3D images to 3D models is today typically using algorithms where the trajectory of view around the object to be scanned is either well known or determined by complicated probability based algorithms like that in Microsoft's Kinect v2 SDK 3D fusion. In practice, these complicated algorithms frequently fail for too un-structured or too complicated objects to be scanned.
State of the art for apparel size determination is to manually measure body dimensions of merit, then looking up retail apparel sizes in simple tables based on such measurements. The manual measurements are performed by flexible measurement tapes, in some shops also with special mechanical gauges.
Only the derivation of shoe sizes is sometimes electrically assisted by X-ray cameras.
In the field of fitness and body building, the measurement of increase of muscular mass or the progress in losing fat is also, as state of the art, measured by mechanical measurement using a flexible tape to determine limb/chest circumferences. An indication on which position the muscle mass is changing (for example ventral/dorsal) cannot be given.
Analysis methods giving this information, and furthermore give a graphically representation thereof, are up to now the domain of sophisticated and extremely expensive medical equipment like computer tomography, ultrasonic analysis, or X-ray layer analysis.
Other fitness/medical parameters like lung volume are, as state of the art, measured by highly expensive special equipment as integrating flux meters and not by 3D body analysis methods.